According to Exodus 20:5 and other verses, God is a jealous God.
Jealousy is so associated with evil that we hesitate to attribute it to God. Without the testimony and authority of Scripture we would never have accused Him of that.
A jealous nature is not one that commands our admiration.
Francis Bacon speaks of envy as the vilest of passions. It distorts everything, blinds the vision, and is the mother of profound unhappiness.
Even the Bible is not ignorant of the darker side of jealousy. Cain and Saul are obvious examples where it causes them ruin. But even in the New Testament we see it in the disciples and certainly in the scribes and Pharisees.
And yet the Bible, which knows our human hearts and searches out the latent evil in them, assures us of the jealousy of God.
We begin to see the solution to the difficulty of a jealous God when we recall the connection of jealousy with love. Jealousy is the shadow cast by love. That is the difference between jealousy and envy.
Envy, the meaner word, is far broader than jealousy. It applies to the intellect as well as the heart. Envy touches relationships where love is never thought of.
A scholar may be envious of another but we don’t say a husband is envious of his wife because marriage is a relationship of love.
God’s essential nature is revealed to us as love. And if that love flows out upon humanity in an infinite and everlasting mercy, it also, if it be deep and mighty, can scarcely lack the attribute of jealousy.
We are finite creatures and such creatures cannot fulfill another completely. So our jealousy tends to become sinful.
Only God can satisfy the heart.
God’s jealousy was also revealed in Jesus. As surely as God will tolerate no rival, Jesus Christ would tolerate no rival. He makes a claim upon the human heart of absolute and unconditional surrender.
Jesus tolerated many things but one thing He NEVER tolerated was the division of His empire (John 5:22; 14:6; Matthew 11:27). God is ONE.
This doctrine was important because of the prevalence of polytheism whose attractions were many. So the idea of a jealous God kept the Israelites true to their spiritual leading.
That thought made the world ready for the incarnation.
A jealous God may be a dark conception, but a jealous God can never be indifferent. Indeed Jesus was so jealous and His love so intense that he braved the cruelty and abuse and humiliation of a cross for us.